• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.73-80
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• 2022

This study evaluated changes in fluidity and rheological properties over time for 3D printed composite materials, and evaluated compressive strength and splitting tensile strength properties for laminated and molded specimens. The composite material for 3D printing starts to change rapidly after 30 minutes of extrusion, and the viscosity of the material tends to be maintained up to 90 minutes, but it was confirmed that construction within 60 minutes after mixing is effective. The compressive strength of the laminated test specimen showed equivalent or better performance at all ages compared to the molded test specimen. In the stress-strain curve of the laminated specimen, the initial slope was similar to that of the molded specimen, but the descending slope was on average 1.9 times higher than that of the molded specimen, indicating relatively brittle behavior. The splitting tensile strength of the P-V laminated specimen was about 6% lower than that of the molded specimen. It is judged that this is because the interfacial adhesion force against the vertical load is affected by the pattern direction of the laminated test specimen.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.193-198
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• 2021

In this study, the rheological characteristics and of 3D printing composite materials and the compressive strength characteristics according to the lamination patterns were evaluated. As a result of rheology test, rapid material change was observed after 60 minutes of extrusion, yielding stress 1.4 times higher than immediately after mixing, and plastic viscosity was 14.94-25.62% lower. The compressive strength of the specimens manufactured in the mold and the laminated specimens were compared, and the lamination pattern of the laminated specimens were 0°, 45°, and 90° as variables. The compressive strength of the mold casting specimen and the laminated specimen from 1 to 28 days of age showed similar performance regardless of the lamination pattern. In particular, at the age of 28 days, the modulus of elasticity, maximum compressive strength, and strain at maximum stress of all specimens were almost the same. In order to analyze the interface of the laminated specimens, X-ray CT analysis of the specimen whose compressive strength were measured was performed. Through CT analysis, it was confirmed that cracks did not occur at the lamination interface, which can be judged that the interface in the laminated specimen behaved in an integrated manner.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.244-250
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• 2023

In this paper, mortar mixed with tapioca starch was manufactured to evaluate the effect of tapioca starch on mortar, through evaluating the quality characteristics of mortar, the impact of tapioca starch on improving the performance and basic quality of mortar was examined. Tapioca starch tended to decrease flow by increasing the viscosity of the dough consistency of fresh mortar, which tended to reduce flow, and decreased by about 10 % as the tapioca starch mixing ratio increased by 0.025 %. In addition, the effect of tapioca starch on the compressive strength of mortar was at the same level regardless of the tapioca starch mixture at 28 days of age. However, at an early age of 3 days, the speed of compressive strength development was accelerated by mix ing tapioca starch. In addition, the effect of tapioca starch on the compressive strength of mortar was at the same level regardless of the tapioca starch mixture at 28 days of age. However, at an early age of 3 days, the speed of compressive strength development was accelerated by mixing tapioca starch. The speed of strength development improved by about 20 % when mixing 0.050 % tapioca starch. The adhesion strength improved by about 60 % when mixing 0.050 % tapioca starch, and the final shrinkage in length change decreased by 5 %.

• Membrane Journal
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• v.33 no.6
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• pp.439-446
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• 2023

Ceramic membranes are generally used for various industrial processes operating under extreme conditions because of its high thermal and chemical stability. However, due to the trade-off phenomenon of permeability and mechanical strength, preparation of high permeability-high strength membrane is necessary. In this study, the change in characteristics and performances of ceramic membranes was analyzed depending on the type of polymer binder and its mixing ratio. Because the solubility between solvent and polymer binder was higher in PSf (polysulfone) than in PES (polyethersulfone), the viscosity and discharge pressure of the PSf-based dope solution were higher than those of PES-based dope solution. When PSf was used as a polymer binder, ceramic membrane showed high mechanical strength and low water permeability due to the dense structure. On the other hand, in case of PES, the mechanical strength was slightly reduced and the water permeability was increased. It was confirmed that the optimum mixing ratio of the PSf and PES with high water permeability and mechanical strength was 9:1.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.6
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• pp.790-797
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• 2023

Guar gum is an edible starch extracted from Cyamopsis tetragonolobus and used as an auxiliary ingredient to enhance the viscosity and adhesiveness of food and improve its emulsification stability. Here, characteristics of fish surimi mixture with various added amounts (0, 0.23, 0.45, 0.67, and 0.89 wt%) of guar gum were analyzed. In unheated surimi with guar gum, the pH decreased as the content increased. In the color values analysis, only the b^* (yellowness) increased depending on the amount of added guar gum. The firmness increased with increasing guar gum content, and no significant difference in adhesiveness was observed. In heated surimi, a^* (redness) and b^* decreased in a content-dependent manner, and L^* (lightness) was higher than that of unheated surimi. Regarding physical properties, the highest values of hardness, gumminess, and chewiness were observed in the heated surimi with 0.67 wt% of guar gum. However, no significant change was observed in springiness and cohesiveness. Results of sensory evaluation indicated that with higher guar gum content, only the hardness increased slightly, and significant differences were absent in the remaining parameters. Thus, surimi with 0.67 wt% of guar gum is considered to be optimal for 3D printing.

• Journal of the Korean Applied Science and Technology
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• v.41 no.3
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• pp.756-770
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• 2024

This study confirmed emulsion stability after performing antioxidant, whitening, antibacterial, and anti-inflammatory efficacy evaluation to find out the availability of Sicyos angulatus L. (SA) which is designated as an ecological disturbance species as a functional cosmetic material. SA was extracted with Deionized Water (SAW) and 70% EtOH (SAE). Compared to SAW, SAE has excellent antioxidant efficacy by showing scavenging activity and SOD-like activity against DPPH radical and ABTS⁺ radical, and inhibits melanin production by inhibiting the activity of tyrosinase. SAW had no antibacterial effect on Escherichia coli (E.c), Staphylococcus epidermidis (S.e), Staphylococcus aureus (S.a), Pseudomonas aeruginosa (P.a), and Cutibacterium acnes (C.a) strains, while SAE showed antibacterial activity by producing clear zones in E.c, S.e, P.a, and C.a strains except S.a. In LPS-treated RAW 264.7 cells, SAE showed efficacy against anti-inflammatory by inhibiting the production of NO by inhibiting the expression of iNOS and COX-2 than SAW. It was confirmed that the SAE-added emulsion was not separated at temperatures of 4℃, 25℃, and 50℃, the pH and viscosity did not change significantly in numerical terms, and the particle size was similar to that of the control emulsion, so it did not affect the formulation. Based on these results, we suggest its potential as a new material for functional cosmetics research.

• Korean journal of food and cookery science
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• v.29 no.4
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• pp.387-398
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• 2013

Seasoned soy sauce is one of the popular seasoning sauces added to the Korean traditional foods such as Bulgogi, Galbi. However, industrially processed sauces have poor sensory quality because of heating treatment for sterilization. The purpose of this study was to develop seasoned soy sauce having fresh taste and good quality by applying superheated steam (SHS) and high hydrostatic pressure (HHP) technologies. To maintenance the sauce qualities, food materials such as apple, onion, and garlic were pretreated with SHS (heater $100^{\circ}C$, steam $280^{\circ}C$, 30 s~1 min 30 s) before mixing with other ingredients. During storage of 7 days, color, pH, and browning potential of SHS treated samples (apple, onion and garlic) did not change and also polyphenol oxidase was inactivated (p<0.05). The seasoned soy sauce including SHS treated materials was sterilized by thermal process ($85^{\circ}C$, 30min) or non-thermal process, HHP (550 MPa, $5{\sim}10^{\circ}C$, 3 min). In SHS+HHP treated sauce, salinity, sugar contents, lightness, viscosity did not change (p<0.05), and total viable cell counts were detected below 4 log cycle at $5^{\circ}C$ for 30 days. E.coli and B.cereus are not determined in all samples. In sensory evaluation, Bulgogi prepared with SHS+HHP treated sauce was more acceptable than others.

• Korean Journal of Food Science and Technology
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• v.15 no.1
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• pp.12-18
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• 1983

Changes in the quality and amino acid composition of soymilk prepared from soaked and germinated soybeans were investigated. Soybeans were soaked in water for 3 hrs and germinated at $18{\pm}1^{\circ}C$ for 5 days followed by water extraction at room temperature, and then the soymilk was boiled for 30 min. The initial yields of total solid and protein after soaking were 80.7% and 88.6%, respectively and decreased slowly during germination. A slow decrease in lipids and a rapid reduction in total sugar content were found during germination. The change in protein fraction content of soymilk showed an initial increase followed by a gradual decrease. The intrinsic viscosity increased rapidly after 3 days of germination to maximum value at 4th day, then decreased. The amino acid composition of protein fraction of soymilk showed little change while that of nonprotein fraction changed significantly. After 4 days of germination, aspartic acid and alanine increased more than twice, and methionine and tyrosine decreased to half of their initial composition in soymilk prepared from soaked soybean.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.365-371
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• 2013

Purpose: In this study, we evaluated the physical and thermal properties of the compositions made by blending glass fiber (GF) of different contents into glass fiber polyamide-66, and investigated if the compositions applying to the glasses frame to replace the TR-90, which is polyamide-12 resin used as an injection-type spectacle frame material. Methods: To investigate the characteristics change of polyamide-66 (PA-66) compositions with the change of the content of glass fibers, we produced a composition of the content by using a twin-screw extruder. The mechanical strength of the composition production was measured and coating properties as well as cutting processability were evaluated. We evaluated the applicability of the glasses frame by comparison the results of new compositions with characterizations of traditional TR. Results: For the results of the characterization of Polyamide-66/GF composition, we found that the higher increase of content of the glass fiber, the less mold shrinkage rate, and the mechanical strength was increased. Tensile strength increased from $498kg/cm^2$ for 0 wt% of the content of the glass fibers to $849kg/cm^2$ for 30 wt% of the content of the glass fibers. As a result of a coating evaluation, the strength of coating was 4B in the GF 5wt% and 5B, which was extremely good coating characteristics, in the over than GF 5 wt%. Conclusions: In case that 30 wt% of the glass fiber was blended, the mechanical strength was greatly improved, the hardness was increased, injection temperature increased due to increase of the viscosity, and the flow mark of the product may occur. The paint coating of PA-66 blended with glass fiber was all excellent. With general evaluating physical properties and workability properties it was determined that around 10 wt% of the content of the glass fibers was possible to apply a spectacle frame.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.4
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• pp.361-368
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• 2021

The objective of this study was to establish technology for removing bacteria with human- and eco-friendly material. Staphylococcus aureus as an important component for balanced equilibrium among microbiomes, was cultured under various concentrations of phosphate. Experimental observation relating to physical properties was performed in an addition of phosphate buffer. Statistically minimum value of size and hardness using atomic force microscope was observed on the matured biofilm at 5 mM concentration of phosphate. As a result of absorbance for the biofilm tagged with dye, concentration of biofilm was reduced with phophate, too. To identify whether this reduction by phosphate at the 5 mM is caused by counter ion or not, sodium chloride was treated to the biofilm under the same condition. To elucidate components of the biofilm counting analysis of the biofilm using time-of-flight secondary ion mass spectrometry was employed. The secondary ions from the biofilm revealed that alteration of physical properties is consistent to the change of extracellular polymeric substrate (EPS) for the biofilm. Viscoelastic characterization of the biofilm using a controlled shear stress rheometer, where internal change of physical properties could be detected, exhibited a static viscosity and a reduction of elastic modulus at the 5 mM concentration of phosphate. Accordingly, bacteria at the 5 mM concentration of phosphate are attributed to removing the EPS through a reduction of elastic modulus for bacteria. We suggest that the reduction of concentration of biofilm induces dispersion which assists to easily spread its dormitory. In conclusion, it is elucidated that an addition of phosphate causes removal of EPS, and that causes a function of antibiotic.